The OOM Manuals for my HT20D and HDT1000, which uses the Eaton 11 hydro both state:
Do not drive the tractor immediately after start up. Let the engine run
a few minutes to allow hydrostatic fluid to warm up first. ln extreme
cold weather the tractor should not be driven until the hydraulic lift
system is operating. Length of warm up will be determined by
temperature.
In the 1996 Service Seminar Book there is a list of Hydraulic fluids that are recommended for the Eaton 11:
DIESELTRACTOR AND 2-SPEED GASTRACTOR
TRANSMISSION/HYDRAULIC OIL CROSS REFERENCE
The following is a list of transmission/hydraulic fluids which may be substituted for the original factory-supplied oil when
you add or make routine transmission oil changes.
Allis Chalrners HPF821 Power Fluid
Amoco 1000
Atlantic Richfield Arco Tractor Ruid
J.I. Case TFD Fluid
Cheveron Tractor Hydraulic Fluid
Conoco Power·Tran II Fluid
John Deere Type 303 Special Purpose Oil
Exxon Torque Ruid 56
Ford 134 Tractor Hydraulic Fluid
Garden Way 1738157 (gal.)
International Hy-Trans Fluid
KendalL Hyken 052
Lion HT Fluid
Massey-Ferguson M-1127 Perma-Tran Fluid
Mobil Mobil fluid 424
Oliver Oliver 55 Fluid
Pennzoil. Hydra-Tranz & Wet Brake Fluid
Phillips HG Fluid
Ouaker Tractor HydrauliclTrans. Fluid
Shell Donnax T-4
Texaco TDH Oil
Union HydrauliclTrans. Fluid
Valvoline Unitrac
White 0-1722